Judge Calls Testimony of Anti-Roundup Experts "Shaky"

A lawsuit claiming Monsanto Co.’s popular weed killer Roundup causes cancer was dealt a blow by a judge’s conclusions that the opinions of the experts testifying against it are "shaky," a potentially devastating development for the case getting to trial.

U.S. District Judge Vince Chhabria is the first judge to weigh in on the toxicity of the world’s most popular herbicide, the source of a heated debate among scientists and regulators worldwide for more than 30 years. Any key witnesses who are cut from the lineup may profoundly shape the outcome of more than 300 lawsuits collected before the judge -- all the cases in federal courts that seek to hold Monsanto liable for its failure to warn about the risks of using Roundup.

The judge heard from about a dozen witnesses including toxicologists, statisticians and an oncologist. But he took an especially keen interest in a couple of epidemiologists who study how humans contract disease.

“I do have a difficult time understanding how an epidemiologist in the face of all the evidence that we saw and heard last week” can conclude that glyphosate “is in fact causing” non-Hodgkin lymphoma in human beings, Chhabria said in San Francisco court Wednesday. “The evidence that glyphosate is currently causing NHL in human beings” at current exposure levels is “pretty sparse,” he said.

Which witnesses will testify at trial on behalf of more than 700 farmers, landscapers and gardeners claiming that exposure to glyphosate -- through skin contact or inhalation -- caused their non-Hodgkin lymphoma remains to be seen.

Chhabria singled out Beate Ritz, a public health professor at the University of California at Los Angeles, for having conducted independent analysis. Still, Chhabria described her conclusion that glyphosate is currently causing NHL in humans “dubious.” He gave a strong indication that Ritz may be the only witness he allows to testify for the plaintiffs, and that even she is at risk of being eliminated.

Monsanto isn’t completely off the hook, based on what Chhabria said Wednesday. At this stage of the case the judge is acting as a gatekeeper to exclude evidence not backed by scientific rigor, and evaluating whether the witnesses are qualified as experts to present their conclusions to a jury. The judge’s role is to decide whether the testimony is “in the range of reasonableness,” not to decide whether glyphosate causes cancer.

The judge said he’s concluded after the hearings that epidemiology is a “loosey-goosey” and “highly subjective field.” Because of constraints with regard to eliminating witnesses, that may leave room for Ritz to testify, Chhabria said. Maybe Ritz “is operating within the mainstream of the field,” he said. “Maybe that means it’s up for the jury to decide if they buy her presentation.”